geer > 2000 > poster > synthesis on the impact of 20th century water-management and land-use practices on the coastal hydrology of southeastern florida > saltwater intrusion in the surficial aquifer
Synthesis On The Impact of 20th Century Water-Management And Land-Use Practices On The Coastal Hydrology Of Southeastern Florida
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Chloride concentration graphs show the concentration of chloride in selected wells. These graphs illustrate temporal encroachment of interface in southeast Florida. The mapped 'red' line illustrates the modern-day position of the salt-water interface. Sparse chloride data are available prior to 1939 and the regional predevelopment position of the interface is considered uncertain. Intrusion of saltwater in southeast Florida can be partly attributed to construction of drainage canals, that in turn, lowered water levels within the underlying aquifer. In areas where salinity control structures are located near the coast, intrusion does not generally extend far inland. Intrusion is can be locally attributed to the seepage of seawater from tidal canals; movement of the interface has been induced locally by large ground-water withdrawals from coastal well fields.
Palm Beach County
Withdrawals from coastal well fields, elevated ground-water levels, and the effect of canal drainage system represent principal factors influencing the movement of the interface in Palm Beach County. The Lake Worth Drainage District maintains ground-water levels as much as 15 feet above sea level utilizing a system of pumps, control structures, and equalizing canals. The influence of saltwater intrusion is less largely due to maintenance of high water levels within nearby canals.
The saltwater interface lies well inland along the North and South New River Canals in east-central Broward County where control structures have been constructed far inland. Movement of the interface in Broward County is similarly attributed to construction of drainage canals accompanied by a reclamation, lowering of the ground-water table, and of marginal wetland areas to land suitable for development. Intrusion near Hallandale is attributed canal construction in an area of low topography. Intrusion near Pompano is the likely result of canal drainage and well field withdrawals. Inland movement of the interface appears to have stabilized near the Ft. Lauderdale well field, probably due to the location of salinity control structures.
The South Dade Conveyance system helped mitigate overdrainage in southeastern Dade County, and has stabilized movement of the interface that occurred prior to and during the 1960's. Well field withdrawals and management of canal stages are principal factors affecting the movement of the interface in south-central Miami-Dade County. Movement of the interface continued in the 1980's as evidenced at G-901 and G-432, and possibly due to well withdrawals at the Alexander Orr well field. Contamination of Hialeah-Miami Springs well field by salt-water intrusion has been an issue of concern since the late 1930's and is attributed to the influence of tidal waters contained the Miami River Canal, Tamiami Canal, as well as the position of saltwater interface. Construction of tidal structures has helped to limit the effect of tidal waters located south and east of the well field. A decrease in chloride levels during the 1980's may be attributed to a reduction in well withdrawals. The canal system is a major factor affecting movement of the interface in northeastern Dade County. Northwest movement of the interface that occurred during a 25-year period is observed in observation wells located immediately north of the Biscayne Canal. A decline in chloride concentrations at G-894 is attributed to shut down of the North Miami well field between 1977 and 1982.
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Last updated: 04 September, 2013 @ 02:07 PM (KP)